An existing miniature circuit breaker (hereinafter referred to as circuit breaker), serving as a line protection element, has been widely used. Its number of mass production is bigger and bigger and its application fields are wider and wider. As a result, a higher demand on the stability of the working performance of the circuit breaker is raised. From the most basic working requirement of the circuit breaker, the working performance of the circuit breaker includes acting characteristic, operating characteristic and breaking characteristic. However, the basis to measure the stability of the circuit breaker is mainly associated with the time; for example, the acting characteristic of the circuit break is mainly represented on time stability of the time-delay characteristic, long duration of the operating characteristic, and short breaking time. The acting characteristic of the circuit breaker needs to be realized by virtue of a release in an operating mechanism. When trigging one acting characteristic of the circuit breaker, a latch assembly in the last link of the operating mechanism needs to be pushed finally to unlock the mechanism no matter how many links are transferred in the process. It follows that the stability of the acting time of the latch assembly in the operating mechanism of the circuit breaker plays a decisive role in the time stability of the acting characteristic. The long-term actionable characteristic of the circuit breaker also needs to be realized by the reliable fit between a connecting rod and the latch assembly in the operating mechanism. The breaking characteristic of the circuit breaker is to further shorten the breaking time by virtue of an arc extinguish chamber in the circuit breaker except for being related to the acting time of the latch assembly in the operating mechanism. It is apparent that the acting characteristic, the operating characteristic and the breaking characteristic of the circuit breaker are closely related to the stability of the acting time of the latch assembly.
The prior art starts from improving the stability of the acting time of the latch assembly, which is mainly realized through controlling the tripping force of the latch assembly. Since the tripping force is related to a contact pressure produced by the meshing between the connecting rod and the latch assembly in the operating mechanism, the tripping force needs to be controlled and decreased in order to ensure said stability of the acting time of the latch assembly. At present, there are two schemes that are commonly used to control and decrease the tripping force: one scheme is to control the tolerance of the force or torque produced by various springs in the operating mechanism, i.e., to ensure the consistency of the contact pressure produced from the fit between the connecting rod and the latch assembly in the operating mechanism through a spring processing technology; and the other scheme is to decrease the tripping force by regulating a force bearing arm to propel the latch assembly as well as regulating a moment arm of the contact pressure produced by the fit between the connecting rod and the latch assembly in the operating mechanism. However, it is failed to achieve satisfactory results of improving the stability of the working performance of the circuit breaker from the aspect of obtaining a stable tripping force by either using the first or second scheme or jointly using the two existing schemes. The actual application process shows that: since the stability of the acting time of the latch assembly is mainly realized by the size of the tripping force, there will still be inconsistent changes in the tripping force of the same mechanism in each time. The tripping force is fluctuated in disorder when continuously closing after releasing the operating mechanism; and becomes stronger in a constant value when closing and intermittently releasing the operating mechanism. The phenomenon of the tripping force that becomes stronger is in contradiction with the object to improve the stability of the operating characteristic of the circuit breaker, and therefore, the stability of the circuit breaker products produced after the adoption of these existing schemes still cannot meet the specific requirements of the market.
In addition, the stability of the breaking performance of the existing circuit breaker is further express by increasing the arc extinguish ability of the arc extinguish chamber on the basis of ensuring the stability of the acting time of the latch assembly in an auxiliary way. The existing arc extinguish measures in this aspect mainly include: to add a concentrating flux plate in an arc channel to perform magnetic blow-out to elongate the arc; to perform air-blowing on the materials of the arc channel by adding gassing materials at the same time, so as to improve the gas dielectric strength of the arc space; to increase the number of arc extinguish gate sheets to raise the arc voltage; and to improve the exhaust condition at the end of the arc extinguish chamber and control the time of the arc within the arc extinguish gate sheet to limit arcing. All these existing measures have correspondingly increased the breaking ability of the circuit breaker, but have unsatisfactory effects on improving the stability of the breaking characteristic of the circuit breaker; for example, the structure gap between the arc extinguish gate sheets may be broken due to oversize breaking air flow in the breaking process, resulting in the loss of arc extinguish ability or unstable arc extinguish ability of the arc extinguish chamber, and even presenting opposite results between next breaking characteristic and previous breaking characteristic of the circuit breaker to reduce the breaking operation consistency.